Or maybe because the period you mentioned was the peak of his career and he has since diminished. He failed in the CB Series, the IPL, and now in Sri Lanka. The only good tournament he has had was the Asia Cup where the pitches were batting paradises. His fielding is bogus. At this moment in time, he doesn't warrant a spot in the ODI team.
So he's in his peak in 2007 and some bad form (not even that bad) means he should be dropped?!